Method of coating pipe



June 30, 1942. w. R. POS' I'LEWAITE METHOD OF COATING PIPE Original Filed July 30, 1938 3 Sheds-Sheet 1 \N a T on R G [WW/am I? Fasf/ewai/e INVENTOR ATTORNEY June-30, 1942- w. R. POSTLEWAITE 2, 3

METHOD OF COATING PIPE Original Filed July 50-, 1958 .3 "Sheets-Shee t 2 h/lY/lbm- P. Pasf/ewai/e INVENTOR ATTORNEY June so, 1942.

w. R. PosrLEwAtTE: METHOD OF comma .PIPE

Original Filed July 30, 1938 SSheetQ-Sheet 3 Mum fi. Fbsf/ewa/k INVENTOR ATTORNEY I I T ON Patented June 30, 1942 4 METHOD or COATING PIPE William R. Postlewaite, San Francisco, Calif., as-

sig'iior to Standard Oil Company of California, San Francisco, Calif., a corporation of Delaware Original application luly 30, 1938, Serial No.

1940, Serial No. 334,390

9 Claims. (Cl. 18-59) This application is a division of my copending case Serial No. 222,207, filed July 30, 1938, entitled Apparatus for cooling coated pipe.

Heretofore, it has not been considered economi- Divlded and this application May 10,

remain axially centered to receive a uniform thickness of coating.

cal to coat steel pipes and the like of relatively small diameter, fo example, 4 inch nominal diameter and smaller, with thick hot mastic coatings of the type described and claimed in United States Patent No. 1,984,649, issued December 18, 1934 to C. S. McDonald et a1. Extrusion methods such as those of my Patent No. 2,040,876, issued May 19, 1936, have been successfully used on pipes from 4 to 18 inches in diameter, these methods being necessarily slow due to the dimcultyv in cooling the large body of hot material surrounding the pipe and "to the physical handling of,the long and heavy pipe sections, these latter weighing upward of two tons. Smaller pipe requires rapid handling if an adequate amount is to-be economically coated in a given time, and also there is a correspondingly larger demand for it.- Certain-factors, such a: the provision of adequate'couplers for guiding and aligning succeed- .ing joints of pipe through the coating equipment,

cooling the inside as well as the outside of the coated pipe, provision for maintenance of axial alignment of the pipe passing through an extrusion nozzle while n'on-deformably supporting the already coated uncooled and unsupported portion, all combine to presentan entirely different set of conditions for coating small pipe sizes from that imposed by the larger diameters, and have been successfully met by this subject invention.

It is an object of this invention to provide an' improved method and apparatus for the rapid coating of small diameter steel pipe with a thick layer of hot bituminous mastic materials, and particularly for the cooling and subsequent handling of the coated lengths after the actual application of the corrosion resistant sheath.

Another object is to provide an improved method and apparatus for supporting the advancing end of a small diameter and hence limber and flexible pipe so that the part passing through an Another object is to provide an improved method and apparatus for a cooling, and,preferably but not necessarily, a supplemental coating bath which will permit small pipe to' be rapidly passed therethrough with minimum mechanical manipulation and the least damage to the sheath orcovermg.

Another object is to provide a method and apparatus for coating pipe of small diameter that will readily lend itself to parallel or multiple operation, by mounting several units side by side in the same housing and supplying them from a common source of material.

Another object is to provide an improved pipe feeding device that will pass couplers or connectors of larger outside diameter than the nominal diameter of the pipe, without changing the axial position of the pipe upwardly or downwardly, so that it remains in axial alignment with the coating means at all times.

Another object is to provide a coupler for temporarily joining adjacent lengths of pipe being fed forwardly through a pipe coating means that will permit cooling water or other liquid to enter the pipe so as to more rapidly cool the pipe and tion, of a pipe coatingl apparatus showing one form of cooling method and apparatus which may be utilized.

Figure 2 is a side elevation view, partly in section, of an alternative form and mode of operation of cooling apparatus in which the inside of the pipe as well as the outer surface of the coating is exposed to the cooling bath.

Figure 3 is a longitudinal sectional view, to an enlarged scale, of a labyrinth inlet for admittinghot freshly coated pipe below the surface of a cooling bath with minimum liquid loss from the latter.

Figures 4 and 5 are longitudinal sectional views of alternative submerged pipe inlets to a similar,

cooling bath, using inwardly directed liquid jets to reduce liquid loss from the bath.

. Figure 6 is a longitudinal sectional view of a extrusion nozzle or similar coating means will 'couplei" suitable for practicing this invention,

adapted to axially align two lengths of pipe being coated, the following pipe section acting to urge forwardly the leading pipe section. V

Figure 7 is a longitudinal sectional view of an alternative arrangement of cooling bath with a parallel liquid jet arrangement for supporting the freshly coated and uncooled pipe during its traverse of the bath, to prevent deformation of the sheath.

Figure 8 is a transverse sectional view on line VIIIVIII of the jet supporting arrangement of Figure 7.

Figure 9 is a plan view of a pipe driving means and an extrusion nozzle particularly adapted to feed and maintain in proper axial alignment the pipe and couplers being coated with a thick layer of hot mastic material.

Figure 10 is a vertical sectional view ofthe pipe driving means and extrusion nozzle shown in Figure 9, taken on line X-X of that figure.

Figure 11 is a vertical sectional view on line XL-XI of Figure 10 and illustrates resilient guide rollers to keep the pipe and couplers in axial alignment with the extrusion nozzle.

Figure 1-2 is a vertical sectional view on line )HI-XII of Figure 10 and illustrates an arrangement of power driven traction rollers adapted to urge the pipe being coated axially through the extrusion nozzle.

Figure 13 is a side elevation view of one form of resilient pneumatic support for the newly coated and incompletely cooled pipe as it passes through the cooling bath.

Figure 14 is an end elevation view of the pipe support shown in Figure 13, illustrating the soft pneumatic tire which distributes the load along a consider-able length of the still plastic coating to prevent deformation thereof.

Figure 15 is a side elevation'view, partly in section, of an alternative form of cooling apparatus in which a number of suitably arranged electromagnetic elements are used to partially support the coated pipe.

Figure 16 is a side elevation view, partly in sec-, tion, of an alternative form of cooling apparatus in which a dense immiscible liquid such as mercury is used to support the freshly coated pipe.

Figure 1'? is a vertical sectional view on line XVII--XVII.of Figure 16, showing a form of liquid jet for preventing loss of mercury from the cooling bath. Figure 18 is a vertical sectional view on line XVIII-XVIII of Figure 16, showing how the heavy liquid, such as mercury, would serve to support the coated pipe without deformation of the coating layer.

Referring to the drawings and particularly to the general arrangement of Figure 1, reference numeral 20 designates the sections of pipe or other cylindrical objects to be coated successively entering the apparatus from the left end and being urged toward the right a short distance by hand or any other suitable means. Pipe 20 is referably prepared-for coating by being cleaned, dried and coated with a suitable primer, which may be a cut-back asphalt or proper asphaltic composition that has been dried or hardened to form a thinlayer that will soften to establish a bond between the pipe surface and the bituminous mastic to be applied in the extrusion nozzle which will be described below.

Succeeding lengths of pipe 20 are keptin alignment as they pass through the coating equipment by means such as the coupler 2| shown in Figure 6, described and claimed in my copending divisonal application Serial No. 331,849 filed April 26, 1940. This coupler may be secured to the leading section of pipe 20 and provides a cup or receptacle for freely receiving the ad-' v-ancing end of the following section of pipe, for a purpose which will be apparent below. This form of coupler comprises a hollow cylindrical metal body 22 of an internal diameter to freely receive the pipe to be coated. A metal partition I pipe 20 to be coated. When the head of bolt 26 is turned, block 24 is compressed longitudinally and spreads radially to engage the inside of the leading section of pipe 20, thus holding coupler 2| in'place thereon. The end of the next following section of pipe 20 may then be advanced into the chamber at the trailing end of coupler 2|, and is readily removable therefrom after the coating has been applied.

The lengths or sections of pipe 20, aligned by couplers 2| are engaged by the drive means generally designated 28 and are forced axially toward the right into and through a coating means, such as the extrusion nozzle generally designated 29, in which a thick layer of a hot bituminous mastic, for example, is applied. The thickness of the coating usually varies depending upon the nature of the mastic, the diameter of the pipe and the severity of the corrosion producing agents against which the pipe is to be protected, and may range from inch for one inch pipe to /2 inch for four inch pipe. Cou-' plers 2| must obviously be of slightly less thickness thanthe final coating in order to pass the coating means 29.

Referring now to Figures 9, 10, 11 and 12 which illustrate one form of drive means 23 and coating means 29, it will be noted that they are preferably mounted on a suitable base 30 to preserve accurate alignment. Drive means 28, in this example, comprises two pairs of generally concave knurled rolls 3| disposed above and below the pipe 20, each pair supported to move upwardly and downwardly, respectively,

when enlargements such as couplers -2|, pass through the device. This is accomplished by securing the rolls 3| on shafts 32 journaled in upper swinging arms 33 and 34, and lower swinging arms 35 and 38, the bifurcated arms being pivoted at their inner ends on center shafts 31 and 38, which are in turn supported on rigid bearing standards 39. Shafts 31 and 38 carry gears 40 and 4|, the two latter engaging complementary gears 42 secured to the shafts 32 of of arms 34 and 33 are likewise joined by similarmeans, all acting to urge the drive rolls 3| toward the axis of pipe 20 to insure firm contact and positive motion without seriously scarring or damaging the pipe or the primer or other preliminary coating that may be on the pipe.

In operation, assuming the lower center shaft 38 to be the driving shaft, motor 43 would be arranged to turn shaft 38 counterclockwise. Gears 42 and rolls 3| on lower arms 35 and 33 would thus be rotated in a clockwise direction and would urge the pipe to the right, in the direction shown by the arrow in Figure Hi. Upper center shaft 31 would be driven clockwiseby gear 40, andwould in turn, rotate gears 42 and rolls 3| on upper arms 33 and- 34 counterclockwise, to assist the lower rolls in'moving the pipe 20 axially in the direction just mentioned. When a coupler 2| enters the driving means at the left side, rolls 3| on that side will move apart, left upper arm 33 swinging upwardly about shaft 31 and left lower arm 35 swinging downwardly about shaft 38. A corresponding action will take place when the coupler engages the two right hand rolls. After the coupler has passed either set of rolls, they will return to their original spacing. Because of the swinging arm arrangement just described which provides an uninterrupted drive for the pipe and the balanced symmetrical nature of this structure, the axis of the pipe 20 is not disturbed or moved either upwardly or downwardly, so that the alignment with the coating means 29 is maintained.

The drive means just described is primarily adapted to provide axial motion andis not intended to give support to the pipe. Support rolls 46 (Figure 11) made of rubber or similar resillent material are provided for this purpose, and are preferably -sufliciently deformable to absorb the slight enlargement of the couplers 2|. Rolls 46 are preferably made with steel shells 4! journalled on shafts 48 which are vertically adjustable by means of nuts 49 and washers so to be positioned as desired in slots of spaced vertical standards 52.

The coating means 29, in this example, is best shown in Figures 9 and and is of the straight extrusion type, comprising a housing 53 with an axial bore through which the pipe 20 is passed, the inlet 54' being sealed by flexible metal strips 55 and the outlet, which determines the coating thickness, being preferably in the form of a removable tapered sleeve 56 secured to housing 53 as by a threaded collar 51. Hot bituminous mastic 58 is forced into housing 53 as by a suitably driven helical feed screw'59 in cylinder Gil at one side of housing 53. If desired, suitable heating means may be provided for housing 53, to keep the mastic therein from becoming chilled.

The operation of the coating means is believed to be obvious from the drawings. Thermoplastic material 58 is continuously fed into housing 53, for example, at a temperature of 350-450 F. for mastic of a graded mineral aggregate containing 10-15% asphalt, by pump screw 59 and the pipe 20 is likewise continually passed into and through the housing, entering through seal 55 and emerging through sleeve 56 with a;-dense coating 58 which is somewhat soft and plastic at the temperature of application, but which will set to a hard, dense, impermeable layer upon cooling. The couplers 2| will deform flexible strips 55 and will also pass through sleeve 56 so that they will also receive a thinner mastic layer, which may be scraped, melted or chipped off so that the cleaned couplers may be returned to the left end' of the apparatus and installed in uncoated pipe to guide and align it in its passage through the equipment. The couplers also serve to protect the ends of pipe sections 25 as they pass through the coating means to prevent mastic entering the pipe itself, and also act to leave uncoated the ends of the pipe so that they need not be cleaned for threading or welding at the time of installation. The structure of these couplers is claimed in my copending divisional application Serial No. 331,849, flled April 26, 1940, entitled Pipe coating coupler.

It has been found that small pipe, for example 4 inch nominal diameter and smaller,is so flexible and difficult to rack or stack for air cooling of the coating 58 without damage to the latter that such mode of cooling is uneconomical and impractical. Also, liquid spray cooling is little better, due to the quantity of water that must be used and the difliculty of supporting the pipe ing rate to be practicable and economical due to the high speed of cooling, heretofore the limiting factor, and to the possibility of cooling the inside of the pipe as well as the outer surface of the coating, as will be described below for one I embodiment of the invention.

Referring to the embodiment of Figure l, the

hot coated pipe 20 with its layer of mastic'58 emerges from the coating means 29 and enters a tank 6| in which water or'a suspension of hydrated lime in water is maintained by means which will be described. Various means may be employed to control undue leakage or loss .of water at the inlet 62 of the tank 6!, such as the labyrinth of Figures 1 and 3. This comprises a tubev or pipe 63 extending from. inlet 62 toward the coating means 29, and provided with a plurality of circular baifles 64 which clear the'coating 58 on pipe 20 but serve to prevent too much water from flowing back through the annular space that is-left. That water that does escape is caught in trough 55, where it is picked up by a pump 66 and returned through pipe 61 to a cooling tower 68, whence it returns through pipes 69 and ill to the main tank SI for reuse.

As an alternative to the inletsealing means or control just described, Figure 4 illustrates a tube 1| which'extends from inlet a: toward coating means 29 and terminates in an inwardly and forwardly directed annular nozzle 12; Water from any suitable source is introduced into nozzle 12 through pipe 13 and emerges from the nozzle at a rate sufficient to prevent any outward flow from tube H. A second alternative is shown in Figure 5, and comprises an annular pipe I4 set into inlet 62 and provided with a plurality of openings directed inwardly and toward the direction of pipe motion. Water or compressed air is discharged inwardly into tank 6| and it, togetherwith the steam evolved at that point from the hot mastic coating 58 will substantially prevent or control outflow along the pipe.

Referring again to the embodiment of Figure 1, it will be noted that the coated pipe is directed through tank GI and emerges therefrom at I6 at a point above the level of the water or other liquid. It has been found that 4 inch and particularly smaller diameter pipe is so flexible that the deformation thus required is not excessive, and furthermore does not injure the mastic coating at temperatures below 200 F., to which it will be cooled by the water bath. During the passage of the coated pipe through the bath of Figurel,

and particularly near the inlet 62 it is desirable is preferably a wheelbarrow type inner tube and is supported in a suitable bracket 18. The water in tank 6| will serve to prevent sticking of the mastic to the tire and the unit load is preferably maintained low so that no deformation of the still warm and plastic coating will occur.

After the coated pipe has emerged from the tank 8| it may readily be handled on ordinary rolls 19, the coupled sections disengaged and the couplings 2| removed and cleaned for reuse. If hydrated lime is suspended in the cooling water bath, a layer of whitewash will automatically be deposited on the coating and will serve to prevent subsequent sticking of the coated pipe as well as to protect the coating against atmospheric and light eiTects that may be detrimental.

It has also been found that the cooling arrangement of Figure 2 which involves the removal of the coated pipe at a point below the level of the water in tank 6|, and in addition contemplates the separation of the sections of pipe 20 as indicated in that figure, has advantages for certain operating conditions. In this figure, the outlet through which the cooled coated pipe leaves tank 6| comprises a tube 80 in which are disposed a plurality of spaced flexible annular sheets 8| of rubber or the like which permit the passage of the coating 58 but restrict the flow of water. That water that does escape is caught in an elongated trough 82, whence it is picked up by pump 66 and sent to the cooling tower 68 through line 61, being returned to tank 6| through line 10. This embodiment also in-' volves the resilient pipe support means H of Figures 13 and 14. As shown in Figure 2, it may be desirable to separate the coupling 2| from the trailing section of pipe 20, thus permitting water from tank 6| to flow into that section and cool the inside of the pipe, increasing the cooling rate and permitting faster operation thereby. Separation may be accomplished by manually or mechanically pulling ahead the preceding section of pipe and keeping it separated from the trailing section. The unevaporated water that is left in the sections as they leave the bath may be caught in elongated trough 82, as shown at the right end of Figure 2.

Figures 7 and 8 illustrate an alternative form of support for the coated pipe as it is cooled in tank 6 I, in which an upwardly flowing stream of water is used. This may be accomplished by providing a secondary trough 83 in tank 8|, with adjustable side walls 84. Water is forced into "the bottom of trough 83 by a pump 85 and distributed therein by a-pipe manifold 85. The water rises in the confined space between the side walls 84 and overflows into tank 6|, the upward flow tending to float or lift the coated pipe 2|] to maintain its alignment, and also to cool the hot mastic coating 58 so that it will pass out of the tube 80 through sheets 8| without deformation and will be in condition for immediate stacking or other disposal.

Figure 15 illustrates another alternative support for the coated pipe, particularly where a closed tank 81 is used, supplied with cooling water as from pipe 10 and fitted with an outlet seal comprising flexible annular discs 8|. The

inlet seal may be of any of the types previously described or may be a single annular disc 88,

overflowing into a catch basin 65. Tank 81 is constructed of brass or other nonmagnetic mameans to exert an upward force on the steel pipe 20 as it passes through the cooling bath, to almost overcome the weight of the pipe. The lower part of tank 81 may be raised through a part of its length as at 98 so that the coated and partly cooled pipe may bear lightly thereon and so be guided through the bath. Jacks 9| are preferably provided so that the tank 81 may be accurately adjusted vertically to be aligned with the moving pipe 20.

A still further alternative to those described for uniformly and nondeformably supporting the freshly coated pipe in the cooling bath is shown in Figure 16, in which a closed tank 81 is used, and in the lower part of which is a heavy, dense immiscibleliquid such as mercury 92. The mercury in this example will serve adequately to support the coated pipe as shown in Figure 18, and only presents the problem of preventing its loss around the inlet 88. One means of preventing loss of mercury at that point is shown at 93 and comprises a semi-annular jet or nozzle 94 in the lower part of the tank 81, and through which water is passed from pipe 85, to be jetted against the mercury and cause it to pile up as at 9B. Jacks 9| are also of value, to level the closed tank 81 and to accurately align it with pipe 20.

It will be apparent from the foregoing descriptions and the drawings that an improved method and apparatus for applying a thick coating of hot bituminous mastic to small diameter pipe and for rapidly and economically cooling the coated pipe have been disclosed. Obviously, certain modifications and changes could be made without departing from the essential features of the invention, and all such that fall within the scope of the appended claims are embraced thereby.

I claim:

1. A method of continuously coating pipe comprising the steps of continuously advancing a pipe and simultaneously extruding a thick layer of heated thermoplastic material on the outer surface of said pipe, and immediately thereafter, and prior to any contact of said coated pipe with any solid supporting surface, passing said coated pipe below the surface of a liquid bath to cool and harden said coating to a degree where it may be supported without material deformation of said thermoplastic material.

2. A method of continuously coating pipe comprising the steps of coupling successive sections of pipe together to form a continuous portion, extruding a thick layer of heated thermoplastic material on the outer surface, of said continuous portion, and immediately thereafter, and prior to any contact of said coated continuous portion with any solid supporting surface, passing said coated continuous portion below the surface of a liquid bath to cool and harden said coating to a degree where it may be supported without material deformation of said thermoplastic coating material, and then separating said coupledsections.

3. A method of coating pipe comprising the steps of temporarily coupling successive sections of pipe together to form a continuous portion, covering the ends of said sections, extruding a thick layer of hot thermoplastic material on the outer surface of said continuous portion intermediate the protected end sections, and immediately thereafter, and prior to any contact of said coated continuous portion with any supporting surface, immersing said coated continuous porported without material deformation of said thermoplastic coating material, and then separating said coupled sections, and uncovering said pipe ends, said ends being free of coating material so that they may be threaded, welded or otherwise secured together without first having to be cleaned of said coating material.

4. A method of continuously coating pipe comprising the steps of coupling successive sections of pipe together, covering the ends of said sections, extruding a thick layer of hot thermoplastic material on the outer surface of said pipe intermediate the protected end sections, immediately thereafter, and prior to any contact of said coated pipe with any solid supporting surface, passing said coupled sections of coated pipe into a liquid bath to cool and harden said coating to a degree where it may be supported without material deformation of said thermoplastic material, and during the passage of said coupled sections through said liquid bath, separating said sections so that said liquid will enter said pipe and cool the interior thereof. 7

5. A method of continuously coating pipe comprising the steps of extruding a thick layer of hot thermoplastic material on the outer surface of said pipe, and, before deforming said plastic and adhesive coating by contact with any support, immediately passing said coated pipe below the surface of a liquid bath to cool and harden said coating, and supporting only the hardened portion of the advancing end of said coated pipe as it passes through said bath, the trailing portion of said pipe being supported substantially at the point of extrusion of said coating layer.

6. A method of coating a continuously advancing pipe composed of successive lengths temporarily coupled together, comprising the steps of extruding a thick layer of hot thermoplastic material on the outer surface of said pipe, supporting said coated pipe substantially at the point of extrusion before said coated pipe emerges from the coating means, and at a second point removed from said first named point, passing said coated pipe beneath the surface of a body of cooling liquid at a point intermediate said first and second points and without contacting any other solid supporting surface, to cool the coating so that it will be hardened by the time it reaches said second point of support, and separating said successive lengths of coated and cooled pipe.

'7. A method of coating pipe, comprising the steps of temporarily coupling successive sections of pipe together to form a continuous 'portion in such a manner as to cover a short length of said pipe sections on each of the abutting ends thereof to preclude a deposition of coating thereon, extruding a thick layer of hot thermoplastic material on the outer surface of said continuous portion intermediate the protected end sections, and, prior to any contact of said coated continuous portion with any solid supporting surface cooling said coated pipe, separa'ting said successive sections and uncovering said pipe ends,

whereby to provide independent pipe sections a with a continuous coating except for a short length at each end thereof.

8. A method of coating pipe, comprising the steps of temporarily coupling successive sections of pipe together to form a continuous portion in such a manner as to cover a short length of said pipe sections on each of the abutting ends thereof to preclude a deposition of coating thereon, extruding a thick layer of hot thermoplastic material on the outer surface of. said continuous portion intermediate the protected end sections, cooling said continuous portion and while cooling, separating the successive sections and uncovering said pipe ends, whereby to provide independent pipe sections with a continuous coating except for a short length at each end thereof.

9. A method of coating pipe, comprising the steps of temporarily coupling successive sections of pipe together to form a continuous portion in such a manner as to cover a short length of said pipe sections on each of the abuttingends thereof to preclude a deposition of coating thereon, extruding a thick layer of initially plastic coating material on the outer surface of said continuous portion intermediate the protected end sections, permitting said coating to' harden, separating the successive sections and uncovering said pipe ends, whereby to provide independent pipe sections with a continuous coating except for a short length at each end thereof.

WILLIAM R. POS'I'LEWAI'I'E. 

